الفهرس 
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Abstract
This research was designedto compare between lithium disilicate glass ceramic, zirconia and zirconia reinforced lithium silicate glass ceramic as regard weight loss due to a corrosive medium as well as the effect of corrosion on their flexural strength.
Thirty samples were constructed and divided into 3 groups according to ceramic materials used (10 samples for each) group 1(e max ),group 2(Vita Suprinity) and group 3 (BruxzirTM zirconia).
Then each group was subdivided into two subgroups (5 samples each) according to sequence of tests performed .
The first subgroup was weighted then subjected to biaxial flexural strength test .While the second subgroup was first subjected to corrosion test,then weighted and finally subjected to biaxial flexural strength test .
All data were collected,calculated ,tabulated and statistical analysed
Data were explored for normality using Kolmogorov-Smirnov and Shapiro-Wilk tests and showed parametric (normal) distribution.
One-way ANOVA followed by Tukey post hoc test was used to compare between more than two groups in non-related samples. Paired t- test was used to compare between two groups in related samples.
The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM® SPSS® Statistics Version 20 for Windows.
In the corrosion test :
There was a statistically significant difference between (E-Max), (Vita suprinity) and (Zirconia) where (p=0.001).
In the biaxial flexural strength :
There was no statistically significant difference between (E-Max), (Vita suprinity)and(Zirconia) where (p=0.446).